The light-emitting diodes (LEDs) of the solid-state lighting elements have the characteristics of the low power consumption, low heat generation, long operational life, shockproof, small volume, quick response and good opto-electrical property like light emission with a stable wavelength, so the LEDs have been widely used in household appliances, indicator light of instruments, and opto-electrical products, etc. As the opto-electrical technology develops, the solid-state lighting elements have great progress in the light efficiency, operation life and the brightness, and LEDs are expected to become the main stream of the lighting devices in the near future. However, the conventional LED has to be driven by the direct current (DC), and therefore a converter is needed between the conventional LED and the alternative current (AC). The converter has large volume and large weight which leads to cost raising and the wastage of power during the electricity conversion. Therefore, the cost of the conventional LED cannot compete with the present light source.
As the LED technology develops, a bridge-type alternative current light emitting diode structure which can emit light during both positive and negative wave signal-input time of the alternative current is provided. As shown in FIG. 1 and FIG. 2, it mainly takes the advantage of the Wheatstone Bridge and therefore the converter is no longer required. Besides, because the structures of the light emitting diode and the rectifying diode are similar, some manufacture steps can be merged in the same manufacturing step. The space of the rectifying part of the light emitting diode device and the manufacturing steps of the light emitting diode device can be saved and the light emitting efficiency of the light emitting diode device can be enhanced.
As shown in FIG. 1 and FIG. 2, FIG. 2 discloses a circuit design 100′ of a bridge-type alternative current light emitting diode device and FIG. 1 discloses the structure of the light-emitting diode device 100 in accordance with the circuit design 100′. The light emitting diode device 100 includes a substrate 10, a rectifying unit 11 formed on the substrate 10, and a first conducting terminal 12 and a second conducting terminal 13 respectively receiving the external transmitting power signal. Wherein, the rectifying unit 11 includes a plurality of light-emitting diode groups 101, 102, and 103 arranged in accordance with the Wheatstone Bridge circuit arrangement between the first conducting terminal 12 and the second conducting terminal 13. While the alternative current signal is inputted from the external power source, in accordance with the design of the circuit, when the input signal is a positive half power cycle, the first light-emitting diode group 101 emits light; when the signal is a negative half power cycle, the second light-emitting diode group 102 emits light; and the third light-emitting diode group 103 disposed in the central portion of the Wheatstone Bridge circuit emits light during both positive and negative half power cycles.
In order to achieve higher light emitting efficiency of the light emitting diode device, in the arrangement of the device structure, the number of the light emitting diodes in the full-time emitting light-emitting diode group 103 (the third light-emitting diode group 103) is increased. However, in the aspect of the circuit design, no matter how many the light emitting diodes in the third light-emitting diode group 103 are, it is still necessary for the rectifying first light-emitting diode group 101 and the rectifying second light-emitting diode group 102 located at two sides of the light emitting diode device to be electrically connected to each other.
As shown in FIG. 3, when the number of the light emitting diodes in the third light-emitting diode group 103 in the central of the light emitting diode device 300 is increased, the light-emitting diode groups 101, 102, or 103 need to change their structures accordingly. In this situation, the shape of the light emitting diode becomes long and narrow and the light emitting area is reduced. Besides, because the connecting relationship between the light emitting diodes does not change, the modification of the device structure is limited.